Self-centering shaft seal system

Abstract

A seal assembly is undersized in relation to the bore in which it is installed to permit radial floating of the seal assembly within the bore to enable precise coaxial alignment between the seal assembly and shaft, despite misalignment between the axis of the shaft and the axis of the bore. A retaining ring urges a face seal of the seal assembly into static sealing engagement with the stepped face of the bore to prevent leakage of the fluid around the seal assembly.

What is claimed is:  
     
       1. A self-centering shaft seal system comprising: 
       a housing formed with a bore having a generally cylindrical wall of predetermined inner diameter disposed about a bore axis and an annular sealing shoulder disposed transverse to said axis;  
       a shaft supported for rotation within said bore having a generally cylindrical outer running surface disposed about a shaft axis;  
       a seal assembly disposed about said shaft having a metal carrier, at lease one radially acting shaft seal element mounted on said carrier about a longitudinal seal axis in dynamic sealing relation to said outer running surface of said shaft, and a face seal disposed axially between said carrier and said transverse sealing shoulder of said housing;  
       said seal assembly being radially undersized in relation to said bore wall in such manner as to define a radial clearance gap between said carrier and said bore wall free of radial obstructions that would prevent radial movement of said seal assembly relative to said bore wall so as to enable said shaft seal to support and center said seal assembly coaxially on said shaft including when said shaft axis is misaligned with said bore axis through corresponding radial displacement of said seal assembly within said bore of said housing, said face seal including a radial lip portion fixed to and projecting radially inwardly of said carrier and sealingly engaging said shaft in axially and radially spaced relation to said at least one shaft seal element.  
     
     
       2. The system of  claim 1  including a retainer acting forcibly between said housing and said seal assembly to urge said face seal toward constant static sealing engagement with said sealing shoulder of said housing. 
     
     
       3. The system of  claim 2  wherein said retainer comprises a snap ring. 
     
     
       4. The system of  claim 3  wherein said housing includes a snap ring groove, said snap ring being mountable in said groove following said installation and centering of said seal assembly on said shaft to urge said face seal into said sealing engagement with said sealing shoulder and to support said seal assembly in said centered condition relative to said shaft. 
     
     
       5. The system of  claim 1  wherein said face seal is fixed on said carrier. 
     
     
       6. The system of  claim 1  wherein said face seal is separate from said carrier. 
     
     
       7. The system of  claim 6  wherein said face seal has a radially outer surface engaging said bore wall and a radially inward surface spaced radially from and unsupported by said carrier so as to maintain independence of radial movement of said carrier relative to said separate face seal. 
     
     
       8. The system of  claim 1  wherein said face seal includes at least a portion fabricated of polytetrafluoroethylene engaging said shoulder of said housing. 
     
     
       9. The system of  claim 1  wherein said at least one shaft seal element comprises a member fabricated of polytetrafluoroethylene having a lip thereof that is axially bent and extends along said shaft. 
     
     
       10. The system of  claim 1  wherein said clearance gap is free of any radial seals that would completely bridge said gap between said carrier and said bore wall and restrict freedom of said radial movement of said seal member relative to said bore wall.